Automatic knee-locking device



H. W. SPROULS AUTOMATIC KNEE ALOCKING DEVICE Feb. 23, 1937.

Filed July 17, 1935 2 Sheets-Sheet l nvcnlor I/qltorvney y Feb. 23, 1937. H, W SPROULS 2,071,711 .I

l AUTOMATIC KNEE LOCKING DEVICE Filed July 17, 1935 2 Sheets-Sheet 2 Invcnlor llomey i Patented Feb. Z3, 1937 Y'UNTED ST PATi 1 Claim.

' This invention Y relates broadly to artificial limbs and is primarily concerned with a device for use with an artificial leg to automatically lock the knee vof the leg in a manner to prevent the same from buckling forward, causing the wearer to fall.

The invention together with its objects and advantages will be best understood from a study of the following description taken in connection with the accompanying drawings wherein:

'Figure l is a sectional View through the leg with they-knee locking' device released,

Figure 2- is a sectional View taken substantially at right angles to Figure l.

Figure 3 is a plan view of a ring and associated parts.

Figure 4 is a fragmentary detail sectional View through the structure shown Ain Figure 3.

' Figure 5 is a sectional view taken substantially at right angles to Figure 4.

Figure 6 isa perspective' View of an arcuate rack bar, certain parts being broken away and shown in section.

Referring to the drawings by reference numerals it will be seen that the limb comprises a-socketlll for thereception of a stump, a leg portion and a foot portion |2. At the knee thereof the leg is suitably cut away as at 3 to receive the knee portion of the stump l0, and at the knee the stump I and leg are pivotally connected together through the medium of a pivot pin lli which normally permits a free swinging movement of the limb at the knee.

Within the upper portion of the leg is a ring l secured in position through the medium of rivets I6. Extending inwardly from the ring I5 is a bracket plate l1 that merges into an upstanding bumper bar I8. The bumper bar I8 yextends upwardly into a notch I9 provided in the socket l0 at the knee, and at its upper end the bar is provided with a suitable eye |80. to accommodate the pivot pin |4. As thought to be clear from a study of Figure 1 the bumper bar I8 will limit swinging movement of the members Ill and relative to one another.

At the ankle the leg and foot |2 are pivotally connected together as at 20. At the instep the foot I2 is formed to provide a socket 2| and the leg is formed to provide an extension 22 that is adapted to engage the socket 2|. Arranged in the socket 2| between the confronting faces of the walls of the socket and the extension 22 is what may be termed a cushion member 23, the same being formed of rubber or other suitable material. Also, at the ankle joint the leg il and the heel of the foot I2 are suitably vgfooved to accommodate the ends of a second vcushion pad 524 of rubber or other suitable material. Due to the inherent resiliency thereof,

the cushion pad 24 has a tendency to normally l separate the leg and foot I2 at the heel as suggested inA Figure 1.

At the open side of the notch I9 the opposed walls thereof are provided with semi-circular Ygrooves in which are fitted and secured by screws or otherfastening elements 25 arcuate rack bars 2G, 26a'. As also shown in Figure l the walls of the notches intermediate the ends of the respective rack bar accommodating grooves-are provided with sockets for receiving centering pins 2l provided on the concave edges of the respective rack bars.

Cooperable with the rack bars 26, 26a,y are long and short dogs 28, 28a, secured to the ends of a pivot pin 29 extending through` a suitable lug provided therefor on the bracket The dogs 23,- 28d are normally urged downwardly out of the path of the rack bars 26, 26a, through f the medium of suitably anchored spring 30.

Connected at one end with the dogs 28, 28a, are push rods 3| which at their lower ends merge into wish bones, the branches 32 and 34 of the respective wish bones extending through suitable openings provided in the angle portion of the leg At their free ends, the branches 32 of the respective wish bones are equipped with plugs 33 threaded into suitable sockets provided therefor in the heel part of the foot I2. The branches 34 of the wish bones extend through openings also suitably provided in the heel portion of the leg and are provided at, their free ends with plugs 35 which are threaded into sockets provided therefor immediately forwardly of the heel of the foot as shown in Figure 1. The plugs 33, 35 serve for adjusting the rods 3| for regulating the arc through which the dogs 28, 28a are to move into and out of engagement with the rack bar 23, 26a.

It will be noted from a consideration of Figure 1 that the teeth of the rack bars 26, 26a are so arranged as to permit some bend at the knee as in natural walking before a contact of the dogs 23, 28a, with the teeth of the rack bars 26 will be made.

From the above it will be apparent that in ac tual practice when, as in walking, pressure is placed on the foot I2 at the toe thereof the rubber cushion 23 will be compressed with the result that the rods 3| will move in the direction of the knee of the limb thus swinging the dogs 28, 28a in a counter clockwise direction against the actions of springs 30 for positioning the dogs in the path of the teeth of the rack bars 2E, 26a. As the knee bends, as is natural in the act of walking, the dogs 28, 28a being in this last named position, said dogs will engage in a manner hereinafter fully described with the teeth of the rack bars 26, 26a holdingthe knee from buckling forward until pressure is taken oi the foot I2 at the toe thereof.

Similarly when presure is applied to the heel there will be a relative swinging movement between the foot l2 and the leg Il causing the cushion 24 to contract and the rods 3l to be pushed upwardly to swing the dogs 28, 28a in a counter clockwise direction for again engagingthe rack bars 26, 26a to lock the knee joint and thereby prevent forward buckling of the articial limb at the knee.

In connection with the above it is to be noted, and as before stated, that one of the dogs, 28a, as shown, is longer than the dog 28. In this connection it is to be further understood that the improved knee lock provides for the locking of the limb in a straight line at any angle up to 45 degrees, and further that the notches in the rack bars 2E, 26a are so spaced that when the weight is put on the heel the longer of the dogs 28a cornes into contact with the first notch on its rack bar 26a, if the leg is in a straight line.

If the leg is bent or buckled ahead, the said dog 28a will Contact with the next or one of the next notches. If there is any weight on the heel of the foot the conditon indicated will obtain. If there is no weight on the heel of the foot the leg will rock forward until it passes center when the pressure is put on the ball or toe, causing the push rod 3l to raise the said dog 28 into contact with the rack bar l' locking the leg in a manner to prevent buckling thereof at the knee and thereby safeguard the wearer from falling.

Under normal conditions the longer dog 28 .comes into contact with its rack bar 26a as the Awearer steps forwardly and as he advances, the

said comparatively long dog is dropped back and as wearer comes on o-ver forward onto the toe,

the short dog 28 rises into contact with its rack bar 26 about an inch ahead of the rst tooth on its rack bar. This slight play between the said dog and the rack bar allows the leg to bend at the knee or break as is natural in walking.

From the above it will be apparent that with a limb of this character, natural knee action may be obtainable without danger of the limb buckling forward at the knee. Buckling forward of the limb at the knee often results in causing the wearer to fall and for this reason articial limbs have become very objectionable.

This application is a continuation in part of my prior application Ser. No. 727,356, filed May 24, 1934.

Having thus described the invention, what is claimed as'new is:

In an artificial limb of the character described, a stump socket, a leg, a pivot joint between the socket and the leg at the knee and disposed above the leg, a foot, a joint between the leg and the foot at the ankle, and means controlled by the relative movement of the leg and foot at the ankle for locking the knee joint to prevent buckling of the limb at said joint upon shifting of the weight to the toe or heel portion of the foot, and for automatically releasing the knee joint upon release oi` the Weight, said locking means including arcuate rack bars secured to the pivoted end of the stump socket, dogs pivotally mounted within the leg and engageable with the rack bars upon relative movement of the leg and stump in the bending of the limb at the knee for locking the joint at the knee against buckling forwardly, one of said dogs being longer than the other, and means for moving the dogs into and out of engagement with the rack bar incidental to the action taking place at the ankle joint of the limb incidental to walking, said last named means including a pusher extending through the leg and connected at one end with said dogs, and having a free end provided with divergent branches extending through openings in the leg at the ankle at opposite sides thereof.

HUGH W. SPROULS. 

